Note that the probability of emitting more than one neutron is highly
suppressed, so multiple neutron emission is usually neglected. The
formula (REF ) has been widely used [1]}, [2]}, [3]}, [4]}, [5]}, [6]}.
Other choices are \(\mathcal {P}(b_{T})\simeq w\)  [4]}
and \(\mathcal {P}(b_{T})=w\exp (-w)\)  [1]}, [9]}, [2]}, [4]}, [6]}.
In this work, we choose (REF ) in our numerical calculation.
